The present invention relates generally to double-sided turning inserts for turning operations and, more particularly, to indexable double-sided turning inserts for turning operations and a turning tool.
It is known to provide multiple cutting edges on cutting inserts to permit the inserts to be indexed to use a different one of the cutting edges when one becomes worn or damaged. It is also known to provide chipbreakers on cutting inserts to facilitate breaking chips that are formed from the workpiece as the cutting edge performs its cutting operation. For heavy machining operations, it is typically necessary to have large support surfaces on the insert for stability. Consequently, it is typical that an insert intended for heavy machining applications will be single sided, i.e., have all of its cutting edges on one side of the insert, while the other side of the insert will be used as a support surface. If the cutting edges on the one side of the insert are too close to one another, chips formed from the workpiece by one cutting edge in use can damage adjacent cutting edges. For example, if a single-sided insert has four cutting edges at four corners of the insert, the two cutting edges adjacent the cutting edge that is performing a cutting operation are at a particularly increased risk of being damaged. The usefulness of having chipbreakers as well as large support surfaces imposes particular limitations on the number of cutting edges that can be provided on cutting inserts for use in heavy machining operations.
It is desirable to provide an indexable double-sided turning insert with chipbreakers, large supporting surfaces, and a large number of cutting edges that can be used with a reduced risk of damage to ones of the cutting edges that are not in use.
According to an aspect of the present invention, a double-sided turning insert having a square basic shape with first and second major surfaces, and a side surface between them, comprises exactly four cutting edges proximate exactly four respective chipbreaker structures, wherein each said cutting edge and respective chipbreaker structure is located only at corner portions of the turning insert and spaced from another cutting edge, the double-sided turning insert being provided with exactly two, diagonally located cutting edges on each major surface, the major surfaces being identical but rotated 90 degrees relative to each other.
According to the aspect of the present invention, a double-sided turning insert for turning operations comprises a first major surface having a square basic shape with first, second, third, and fourth corners, a second major surface having a square basic shape with first, second, third, and fourth corners, and a side surface between the first major surface and the second major surface, the side surface including first, second, third, and fourth corners between the first, second, third, and fourth corners of the first major surface and the first, second, third, and fourth corners of the second major surface, respectively, and first, second, third, and fourth side surface portions, each side surface portion of the first, second, third, and fourth side surface portions being disposed between a respective pair of the first, second, third, and fourth corners. A plane of the first major surface and a plane of the second major surface are parallel and are perpendicular to the side surface, the insert comprises first, second, third, and fourth cutting edges and first, second, third, and fourth non-cutting edges, the first cutting edge is formed by the first corner of the first major surface and first corner of the side surface, the second cutting edge is formed by the second corner of the second major surface and the second corner of the side surface, the third cutting edge is formed by the third corner of the first major surface and the third corner of the side surface, and the fourth cutting edge is formed by the fourth corner of the second major surface and the fourth corner of the side surface, and the first non-cutting edge is formed by the first corner of the second major surface and first corner of the side surface, the second non-cutting edge is formed by the second corner of the first major surface and the second corner of the side surface, the third non-cutting edge is formed by the third corner of the second major surface and the third corner of the side surface, and the fourth non-cutting edge is formed by the fourth corner of the first major surface and the fourth corner of the side surface.
According to another aspect of the present invention, a turning tool comprises a toolholder having a pocket and fastening means, a square and flat shim mounted in the pocket, said pocket having upstanding walls defining a bisector, a square and double-sided turning insert having chipbreaker structures and support surfaces on major surfaces thereof, the square turning insert being held against the flat shim by the fastening means, wherein the turning insert is provided with cutting edges only at alternating corners on opposite major surfaces, each chipbreaker structure at a major surface in contact with the flat shim is provided distant from the bisector.
With such an insert and tool it is possible to provide a sturdy indexable insert with four cutting edges that can each perform a turning operation with minimal risk of damage to the cutting edges that are not in use.